The present invention relates to a new and improved method of, and apparatus for, the thermal treatment of impregnated material webs, preferably those impregnated with a settable synthetic resin or plastic material.
Generally speaking, the method of the invention is of the type wherein the impregnated material web is guided in an upward direction through a first heat or thermal treatment zone, then through a deflection or diverting roll arrangement, and thereafter is guided in a downward direction through a second heat treatment zone.
This type drying method and apparatus for performing the same is particularly suitable for the thermal treatment of fleeces and fabrics formed of organic or inorganic fibres, especially glass fibre fabrics, wherein such web-like materials are impregnated with a thermosetting plastic material or resin.
With heretofore known installations of this type employing vertical guiding of the material web the latter is deflected during the thermal treatment processes, i.e. is deflected between the first and second heat or thermal treatment zones. In this way it is possible to maintain the structural height of the installation within acceptable limits. The material web which departs from the first heat treatment zone is however still tacky since the thermal treatment has not been completed. This is accompanied by the danger that the material web might stick upon the deflection rolls. If it were intended to treat the material web in the first heat treatment zone to such an extent that the web, upon leaving such first heat treatment zone, no longer would tend to stick to the deflection rolls, then it would be necessary to correspondingly increase in length such first heat treatment zone, and therefore, there would have to be tolerated an increase in the structural height of the plant or installation or it would have been necessary to move the material web at a correspondingly reduced velocity through the plant. In order to be able to prevent too intensified setting of the impregnation agent in this case, the second heat treatment zone cannot be fully made use of as concerns its temperature.
To prevent sticking of the material web at the deflection or diverting rolls it also has already been proposed to provide an additional cooling device directly before the first deflection roll. This additional cooling device is arranged at the side or face of the material web which comes to bear upon the deflection rolls and blows a suitable cooling medium, for instance air, against this one side of the material web. When the system works at high velocities of movement of the material web it is not possible to effectively preclude, through the use of these measures, that the material web will not become stuck at the deflection rolls.